The prior art relating to automatic watering of flowerpot cultures in large-scale market-gardening establishments comprises the so-called bottom watering, as well as watering according to the flood/ebb principle using water levels being raised and lowered.
When using bottom watering, the flowerpots stand with their perforated bottom on a water-conducting mat constantly being maintained in the wet state, so that the moisture can be absorbed into the pot from below.
With the bottom watering method, there is a risk of a ventilation problem appearing at the lowermost part of the pot due to the fact that the bottom of the pot and the surface of the mat are in close mutual contact. Poor ventilation may cause the filling material in the pot to become acidic or the roots of the plants to rot.
When the flood/ebb principle is used as the watering method, the flowerpots are placed in flat-bottomed tanks with a plane bottom. The tanks are periodically filled and subsequently again drained of water. Compared to the bottom-watering method, the flood-/ebb principle makes it possible to achieve improved control of the proportioning of water and improved control of the desired watering process depending on the specific conditions prevailing.
Even through the desired flood/ebb method implies that water is removed from the tank relatively quickly, it does not necessarily follow that the lowermost part of the filling of the flowerpot will also be freed of excess water sufficiently quickly. The removal of excess water is, however, a prerequisite for good ventilation, especially in the lowermost region of the pot filling. On the other hand, the flood/ebb principle offers the possibility of good air flow to the lowermost part of the pot, as the water is removed quickly from the region around the pot as described above.
It has already been suggested to improve the ventilation conditions by, as mentioned above, providing laterally outwardly facing openings in the lowermost end of the side walls of the flowerpot in the immediate vicinity of the pot bottom. These openings, in addition to letting in water, serve both for removing excess water from the pot filling and to give access for ventilating air to the lowermost part of the pot. Experience has shown, however, that excess water was not always removed and the ventilating conditions in many cases still were unsatisfactory.
In the flowerpot such as described in U.S. Pat. No. 5,010,687 to Hougaard, two distinctly separate bottom regions are provided, each equipped with its own passage opening, so that one of the regions may advantageously be used for one of the watering methods, and the other region for the other watering method. A first region is accurately delimited by the channel-limiting side walls. A second region, likewise accurately defined, exists outside of the channels. Each of the regions mentioned has its own passage opening or openings. The channels make it possible to control the ventilation through the passage openings. The passage openings are situated at a high level in the top wall of the channel. The height of the channels, as measured on the outside wall of the pot, may be made larger or smaller according to desire. Further, it is possible to provide the second region of the pot bottom, situated outside of the channels, with a base-surface area which is selected depending on conditions. This base-surface area of the pot, in the case of bottom watering, may rest on the water-conducting mat over an area of such a size, that the mat is not compressed too much. Finally, the length of the channels may be limited according to desire, making it possible to avoid channel segments unnecessarily reducing the inner space in the pot available for receiving pot filling. The supporting legs serve to stabilize the pot's ability to remain standing.
Experience has shown that problems with the ventilation of the pot filing may arise in flowerpots of the kind such as described in U.S. Pat. No. 5,010,687, when the plants are forced by using ebb/flood watering method. Even though the watering is generally carried out in the desired manner through the channels and the second passage openings situated in the top walls, some water will also seep in or out through the first openings, provided in the bottom of the flowerpot. This seeping in and out will influence a bottom layer of the pot filling substantially situated in the region between the projections formed by the channels and protruding into the side of the pot. Water seeping in through the first openings in the bottom will frequently not carry sufficient quantities of oxygen. Water seeping out through the same path will frequently not cause sufficient drying-out, to make it possible to avoid acidification of the lowermost bottom layer of the pot filling. This inhibits the development of the roots.